The present invention relates to fire protective intumescent curable compositions.
The necessity of protecting steel and concrete structural building materials such as columns, beams, girders and other steel assemblies from the damaging effects of the flames and high temperatures resulting from a fire has been recognized for several years. As a result, a variety of fire protective coating compositions have been developed and tailored for a multitude of applications. The protection of structural steel members and assemblies which remain exposed to climatic elements has been one application area of particular interest. At one time, protection of these structures was accomplished by utilizing cementitous compositions. This posed numerous difficulties; among them, the excessive weight of the cement and the fact that the cement tended to absorb and hold water which inevitably led to corrosion of the underlying steel. More recently, intumescent fire protective coating compositions have grown in popularity. An intumescent coating composition is one which will expand to form an insulating, cellular carbonaceous char structure upon exposure to sufficient heat. For example, U.S. Pat. No. 3,755,223 is directed to an epoxy resin based intumescent composition. Many of the currently available compositions, however, are not without attendant difficulties. For example, often the carbonaceous char will crack and fall off of the substrate rendering it unprotected. To minimize this difficulty, external reinforcement is often required in conjunction with the coating composition thus increasing the cost. Moreover, the composition may not expand uniformly during a fire or, alternatively, it may expand too little or too much thereby diminishing the quality of protection for the underlying substrate. In addition, the intumescent composition may have a tendency for water absorption thus contributing to corrosion of the underlying steel. There is a need, therefore, for an intumescent fire protective composition which upon exposure to flames or excessive heat will produce an integral char which adheres to the steel substrate without the need for external reinforcement while also protecting the substrate from corrosion and other damage brought about by climatic exposure in the event that no fire occurs.